EDEN PRAIRIE, Minn., Aug. 15 (UPI) -- Supermarket chain Supervalu said Thursday it was investigating a potential data breach that could have affected more than 180 stores across the U.S.

The chain, which has more than 3,300 stores, said in a statement data was stolen from cards used at its point-of-sale systems -- cash terminals and registers that handle credit and debit card transactions. The data breach is believed to have occurred between June 22 and July 17, according to a person familiar with the matter.

According to Supervalu, the theft may have resulted in hackers gaining access to account numbers, possibly expiration dates of cards, and other personal information, including the cardholder's name. The company believes cards used at its Cub Foods, Farm Fresh, Hornbacher's, Shop 'n Save and Shoppers Food & Pharmacy stores were affected.

Supervalu says it doesn't currently appear as if any of its Save-A-Lot stores have been affected.

Supervalu said it has secured the part of the network affected by the breach and was using third-party experts to investigate the theft. It encouraged its customers to continue using their cards, as the breech had been contained.

"The intrusion was identified by our internal team, it was quickly contained, and we have had no evidence of any misuse of any customer data. I regret any inconvenience that this may cause our customers but want to assure them that it is safe to shop in our stores," said Supervalu President and CEO Sam Duncan.

The company is working with federal authorities to investigate the incident and also contacted card payment companies, who are cooperating with the investigation.

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